Update branchRuleApprovalProjectRuleUpdate to prevent changing name and approvers of any_approver rules
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=500317) </details> <!--IssueSummary end--> Currently the branchRuleApprovalProjectRuleUpdate mutation accepts name argument to modify the name. For any_approver rules we need to ensure that they cannot do this. I think we can just ignore any values passed without raising any errors.
issue